Reactions of stable amidinate chlorosilylene and [1+4]-oxidative addition of N-heterocyclic silylene with N-benzylideneaniline

Article abstract of DOI:10.1002/ejic.201100661

The reaction of PhC(NtBu)₂SiCl (L) with N₂O afforded the trimer {PhC(NtBu)₂Si(O)Cl}₃ (1), which contains a Si₃O₃ six-membered ring. In the molecular structure of 1, the PhC(NtBu)₂

Full text of DOI:10.1002/ejic.201100661

FULL PAPER
DOI: 10.1002/ejic.201100661
Reactions of Stable Amidinate Chlorosilylene and [1+4]-Oxidative Addition of
N-Heterocyclic Silylene with N-Benzylideneaniline
Anukul Jana,[a] Ramachandran Azhakar,[a] Sankaranarayana Pillai Sarish,[a]
Prinson P. Samuel,[a] Herbert W. Roesky,*[a] Carola Schulzke,[b] and Debasis Koley[c]
Keywords: Boron / Silicon / Chlorosilylene / Cycloaddition / Spiro compounds / Density functional calculations
The reaction of PhC(NtBu)2SiCl (L) with N2O afforded the
trimer {PhC(NtBu)2Si(O)Cl}3 (1), which contains a Si3O3 six-
iPr2C6H3N)2}Si (LЈ) with N-benzylideneaniline resulted in 4,
a [1+4]- rather than a [1+2]-cycloaddition product. Com-
membered ring. In the molecular structure of 1, the pounds 1–4 were characterized by elemental analyses and
PhC(NtBu)2 moieties are arranged around the Si3O3 six-
membered ring in a paddle-wheel fashion. Further the reac-
tion of L with B(C6F5)3 and 9-BBN (9-borobicyclo[3.3.1]non-
ane) yielded the chlorosilylene–boron adducts L·B(C6F5)3 (2)
and L·9-BBN (3). The reaction of CH{(C=CH2)(CMe)(2,6-
spectroscopic methods. The molecular structures of 1, 2, and
4 were established unequivocally by single-crystal X-ray
structural analysis. The formation of products 1 and 4 was
supported by DFT calculations.
as a dehydrochlorinating agent.[3c] Currently there is active
research in the chemistry of NHSis.[6–16] In addition we re-
ported treatment of N2O with PhC(NtBu)2Si–Si(NtBu)2-
CPh which resulted in the formation of two Si2O2 four-
membered rings connected with two oxygen atoms[20] and
also the formation of a stable silaaziridine by reaction of
N-benzylideneaniline with L.[21] Consequently we were eager
to know the reaction of L with N2O and study the reac-
tivity of N-benzylideneaniline with the stable NHSi (LЈ) [LЈ
= CH{(C=CH2)(CMe)(2,6-iPr2C6H3N)2}Si].[3c] Previously,
we had shown N–H bond activation of ammonia,[7b] hy-
drazines,[7c] formation of spirocyclic compounds,[7c,13h] C–
H as well as C–F bond activation of fluoroarenes,[16a] re-
giospecific C–H activation of ylide[16b], and reactivity of
ketones and quinone[16c] with LЈ. Interestingly, the reaction
of L with N2O afforded compound 1 comprising a Si3O3
six-membered ring. N2O has attracted considerable atten-
tion as a precursor for an ideal mono-oxygen donor in oxi-
dative reactions, which proceeds with elimination of dinitro-
gen as the single side product.[20,22] The molecular structure
of 1 features a paddle-wheel arrangement. Further, we re-
ported the chlorosilylene–boron adducts L·B(C6F5)3 (2) and
L·9-BBN (3) by the reaction of equivalent amounts of L
with B(C6F5)3 and 9-BBN, respectively. The reaction of N-
benzylideneaniline with LЈ afforded the [1+4]-cycloaddition
product 4, involving dearomatization of the benzene ring.
In organic chemistry, dearomatizing of arenes provides an
efficient way of generating reactive synthons from inexpen-
sive precursors.[23]
Introduction
Silylenes are neutral compounds with divalent silicon
that are considered to be silicon analogues of carbenes.[1]
Many stable N-heterocyclic silylenes (NHSis)[1b–1d,2,3] have
been prepared after the first report in 1994. The HOMO of
a silylene is nonbonding and possesses nucleophilic charac-
ter. Its LUMO is an empty p-orbital exhibiting electrophilic
character. Accordingly silylenes are considered to have an
ambiphilic character and behave as Lewis acids as well as
Lewis bases.[4] Owing to the presence of both, nucleophilic
and electrophilic reaction centers, the chemistry of silylenes
is quite fascinating.[5–16] The reactivity of NHSis is compar-
able with that of the N-heterocyclic carbenes (NHCs), the
latter having given rise to rapid research activities and nu-
merous applications in chemistry.[17,18] Many highly reactive
compounds with low-valent and zero-valent elements,
which are stabilized by NHCs have been documented.[3b,19]
Recently we synthesized the dichlorosilylene stabilized by a
stable N-heterocyclic carbene (NHC) by employing a new
synthetic procedure comprising the reductive elimination of
HCl from trichlorosilane in the presence of NHC under
mild reaction conditions.[3b]
Furthermore, we reported the synthesis of PhC(NtBu)2-
SiCl (L) in high yield using lithium bis(trimethylsilyl)amide
[a] Institut für Anorganische Chemie der Universität Göttingen,
Tammannstrasse 4, 37077 Göttingen, Germany
E-mail: hroesky@gwdg.de
[b] School of Chemistry, Trinity College Dublin,
Dublin 2, Ireland
[c] Department of Chemical Sciences, Indian Institute of Science
Education and Research-
Results and Discussion
Compound 1 was obtained by adding gaseous N2O to a
toluene solution of L for 10 min at room temperature
Kolkata, Mohanpur-741252, India
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201100661.
5006
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 5006–5013

Reactions of Stable Amidinate Chlorosilylene
¯
Compound 1 crystallizes in the triclinic space group P1
(Scheme 1). Compound 1 is soluble in benzene, toluene, n-
hexane, and THF and it is stable in both the solid state and (Table 1). The molecular structure of 1 is shown in Figure 1.
in solution for a long time without any decomposition un- In 1 all silicon atoms are five-coordinate with τ values (τ =
der an inert gas atmosphere.
1 for perfect trigonal-bipyramidal arrangement; τ = 0 for
perfect square-based pyramid)[24] of 0.78(Si1), 0.77(Si2),
and 0.73(Si3), and are arranged in a distorted trigonal bi-
pyramidal geometry comprising two nitrogen atoms from
the supporting amidinato ligand, one chlorine, and two
oxygen atoms. The Si3O3 six-membered ring is very well
known in silicon chemistry.[25] The PhC(NtBu)2 moieties in
1 are placed in such a way that it gives a paddle-wheel struc-
ture (Figure 1, a). In 1, the PhC(NtBu)2 and Cl moieties are
aligned in the opposite direction to the plane of the Si3O3
six-membered ring (Figure 1, b). The Si3O3 ring in 1 is
slightly distorted from planarity, with the largest deviations
being 0.1108 and 0.1044 Å for atoms O3 and Si3. There
exist two types of Si–N (amidinate ligand) bond lengths,
one being shorter [Si–Nav 1.813(3) Å] corresponding to the
equatorial position and one longer [Si–Nav 2.001(3) Å] to
the axial position. Similarly two types of Si–O bond lengths
are present; the average length of the shorter bond is
1.621(2) Å and the average length of the longer one is
1.670(2) Å. The average Si–O–Si and O–Si–O bond angles
are 136.84(14)° and 100.95(11)°. The average Si–Cl bond
length in 1 is 2.1125(14) Å [Si–Cl of L 2.156(1) Å], and the
N–Si–N cone angles are 67.84(12)°, 67.64(11)°, and
68.39(12)° [N–Si–N of L 71.15(7)°].
Scheme 1. Synthesis of 1.
The 29Si NMR spectrum of 1 shows a single resonance
at δ = –114.51 ppm, which is upfield shifted compared to L
(δ = 14.6 ppm),[3c] because in 1 the silicon atom is shielded
upon attachment of oxygen atoms to silicon. DFT calcula-
tions also reveal a similar upfield shift (Δδcalcd. = 134, Δδexp.
= 129 ppm) for 29Si in 1. The tBu protons for compound 1
1
in the H NMR spectrum display a broad singlet, which is
observed at δ = 1.45 ppm and is shifted downfield com-
pared to that of L (δ = 1.08 ppm). In its mass spectrum
compound 1 exhibits its fragment ions at m/z 629 [M+
–
The reaction of equimolar amounts of L with B(C6F5)3
{PhC(NtBu)2 + 2Cl}] and 594 [M+ – {PhC(NtBu)2 + 3Cl}]. and 9-BBN afforded the colorless crystalline chlorosilylene–
Table 1. Crystal and structure refinement parameters for compounds 1, 2, and 4.
Parameters
1·0.5hexane
2
4
Empirical formula
Formula weight
Temperature [K]
Wavelength [Å]
Crystal system
C48H76Cl3N6O3Si3
975.77
133(2)
C33H23BClF15N2Si
806.88
133(2)
0.71073
monoclinic
C42H51N3Si
625.95
133(2)
0.71073
0.71073
triclinic
triclinic
¯
¯
P1
Space group
P1
P21/n
Unit cell dimensions
a = 8.6167 (17) Å
b = 13.912 (3) Å
c = 23.625 (5) Å
α = 97.99 (3)°
β = 98.86 (3)°
γ = 107.30(3)°
2619.9 (9) Å3, 2
1.237 g/cm3
a = 11.636 (2) Å
b = 18.945 (3) Å
c = 15.316 (3) Å
α = 90°
a = 11.077 (2) Å
b = 12.485 (3) Å
c = 13.109 (3) Å
α = 87.44(3)°
β = 100.36(3)°
γ = 90°
β = 86.97(3)°
γ = 87.99(3)°
Volume, Z
3321.3 (12) Å3, 4
1.614 g/cm3
1807.6 (6) Å3, 2
1.150 g/cm3
Density (calculated)
Absorption coefficient
F(000)
Crystal size
θ range for data collection
Limiting indices
0.288 mm–1
0.265 mm–1
0.098 mm–1
1046
1624
676
0.49ϫ0.17ϫ0.08 mm3
1.56 to 25.95°
–10 Յ h Յ 9, –17 Յ k Յ 17,
–28 Յ l Յ 28
0.19ϫ0.14ϫ0.12 mm3
1.73 to 27.05°
–13 Յ h Յ 14, –24 Յ k Յ 24,
–19 Յ l Յ 19
0.36ϫ0.25ϫ0.15 mm3
1.56 to 27.14°
–14 Յ h Յ 13, –16 Յ k Յ 15,
–13 Յ l Յ 16
Reflections collected
Independent reflections
Completeness to θ
23306
10059 (Rint = 0.0674)
98.0% (θ = 25.95)
29474
15340
7672 (Rint = 0.0590)
95.8% (θ = 27.14)
7236 (Rint = 0.0544)
99.2% (θ = 27.05)
full matrix least-squares on F2
7236 / 0 / 484
1.031
R1 = 0.0465, wR2 = 0.0772
R1 = 0.0765, wR2 = 0.0846
0.290 and –0.266 eÅ–3
Refinement method
Data / restraints / parameters
Goodness of fit on F2
Final R indices [I Ͼ 2σ(I)]
R indices (all data)
10059 / 10 / 591
0.981
R1 = 0.0566, wR2 = 0.1197
R1 = 0.0972, wR2 = 0.1340
0.893 and –0.488 eÅ–3
7672 / 15 / 443
1.010
R1 = 0.0624, wR2 = 0.1349
R1 = 0.1012, wR2 = 0.1515
0.695 and –0.307 eÅ–3
Largest diff. peak and hole
Eur. J. Inorg. Chem. 2011, 5006–5013
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5007

H. W. Roesky et al.
FULL PAPER
equivocally established by single-crystal X-ray structural
analysis.
The coordination of the boron atom to the silicon atom
can be readily noticed in the 29Si NMR spectrum of 2.
Compound 2 resonates at δ = 29.94 ppm with a broad sig-
nal owing to the coupling of silicon with the quadrupolar
11B (I = 3/2) nucleus which is downfield shifted compared
to that of L. The 11B NMR spectrum of 2 exhibits a reso-
nance at δ = –17.55 ppm. The 19F NMR spectrum of 2
shows multiplet resonances centered at δ = –125.38,
–157.47, and –167.73 ppm. The 1H NMR spectrum of 2
exhibits a resonance for C(CH3)3 at δ = 0.65 ppm which is
upfield shifted compared to that of L. Furthermore, 2
shows its [M+ – C6F5] fragment ion in its ESI-MS at m/z
638.
The molecular structure of L·B(C6F5)3 is represented in
Figure 2. Compound 2 crystallizes in the monoclinic space
group P21/n. Both the silicon and boron atoms are four-
coordinate and display a distorted tetrahedral geometry.
The silicon coordination environment is derived from two
nitrogen atoms, one chlorine atom, and a boron atom,
whereas boron features three carbon atoms and one silicon
atom. The silicon–boron bond length in 2 is 2.108(2) Å
which is quite comparable to that in RЈ·B(C6F5)3, {RЈ =
Figure 1. (a) Molecular structure of 1, showing its paddle-wheel
arrangement. (b) Side view of 1 parallel to the plane of the Si3O3
six-membered ring, displaying orientation of PhC(NtBu)2 and Cl
moieties relative to this ring. Selected bond lengths [Å] and angles
[°]: Si(1)–O(1) 1.620(2), Si(1)–O(3) 1.670(2), Si(2)–O(1) 1.668(2),
Si(2)–O(2) 1.620(2), Si(3)–O(2) 1.672(2), Si(3)–O(3) 1.6229(19),
Si(1)–N(1) 1.813(3), Si(1)–N(2) 2.006(3), Si(1)–Cl(1) 2.1062(14),
Si(2)–N(3) 1.808(3), Si(2)–N(4) 2.010(3), Si(2)–Cl(2) 2.1104(14),
Si(3)–N(5) 1.818(3), Si(3)–N(6) 1.987(3), Si(3)–Cl(3) 2.1210(13);
N(1)–Si(1)–N(2) 67.84(12), N(3)–Si(2)–N(4) 67.64(11), N(5)–Si(3)–
N(6) 68.39(12), O(1)–Si(1)–O(3) 100.64(11), O(2)–Si(2)–O(1)
RSiCl2 [R
= 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-
ylidene]} where it is 2.106(6) Å. The Si–Cl distance in 2 is
2.0656(9) Å and the N–Si–N cone angle 72.82(8)°.
100.93(12),
138.30(14),
136.11(15).
O(3)–Si(3)–O(2)
Si(2)–O(2)–Si(3)
101.29(11),
136.12(13),
Si(1)–O(1)–Si(2)
Si(3)–O(3)–Si(1)
boron adducts 2 and 3, respectively in quantitative yield
(Scheme 2). Both compounds 2 and 3 are stable in solution
as well as in the solid state at room temperature in an inert
atmosphere. The chlorosilylene–boron adducts 2 and 3 have
been characterized by elemental analyses and spectroscopic
methods. The molecular structure of adduct 2 has been un-
Figure 2. Molecular structure of 2; the hydrogen atoms have been
omitted for clarity. Selected bond lengths [Å] and angles [°]: Si(1)–
N(1) 1.8110(19), Si(1)–N(2) 1.8126(19), Si(1)–Cl(1) 2.0656(9),
Si(1)–B(1) 2.108(2); N(1)–Si(1)–N(2) 72.82(8), N(1)–Si(1)–Cl(1)
101.94(6), N(2)–Si(1)–Cl(1) 105.67(7), N(1)–Si(1)–B(1) 118.65(9),
N(2)–Si(1)–B(1) 117.09(9).
As for 2, the 29Si NMR spectrum of compound 3 dis-
plays a downfield chemical shift which is observed at δ =
29.62 ppm with a broad signal. The 11B NMR spectrum
of 3 reveals a doublet resonance of equal intensity at δ =
1
–15.04 ppm (JBH = 70 Hz). The H NMR spectrum of 3
exhibits a resonance for C(CH3)3 at δ = 1.01 ppm. Com-
pound 3 shows its molecular ion in its ESI-MS spectrum at
m/z 416. In the IR spectrum we were able to observe the
band for the νB–H vibration at 2193 cm–1 which is in agree-
ment with literature values (νB–H ≈ 2200 cm–1).[26]
Scheme 2. Synthesis of 2 and 3.
5008
www.eurjic.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 5006–5013

Reactions of Stable Amidinate Chlorosilylene
The reaction of LЈ with an equimolar amount of N- keeping the six-membered ring intact and leading to the
benzylideneaniline in n-hexane at room temperature pro- spirocyclic compound 4. In 4, the six- and five-membered
ceeds rapidly with the formation of the dearomatized prod- rings are fused by the silicon center and the resulting rings
uct 4 (Scheme 3). Compound 4 is soluble in n-hexane, n- are arranged nearly orthogonal to each other. The dihedral
pentane, toluene, and benzene. Moreover it is stable both angle between the planes of the six- and five-membered ring
in the solid state as well as in solution for a long time with- is 86.22(5)°. Furthermore, the dearomatized benzene ring is
out any decomposition under an inert gas atmosphere. The not planar similar to those observed in the reaction of LЈ
29Si NMR spectrum of 4 shows a single resonance (δ = with benzophenone[13a] and with diphenyl hydrazone.[7c]
–25.40 ppm) which is upfield shifted when compared with The silicon atom is in a distorted tetrahedral geometry, con-
that of LЈ (δ = 88.4 ppm), because in 4 the silicon atom is sisting of three nitrogen atoms and a carbon atom. Among
more shielded. A similar trend is observed from the DFT the three nitrogen atoms one originates from the nitrogen
calculations (Δδcalcd. = 123, Δδexp. = 113 ppm). The identity atom of the N-benzylideneaniline and the two others from
of the dearomatized product has been clearly established the chelating ligand. The silicon atom is shifted out of the
1
with H NMR spectroscopy, by considerable upfield shift plane defined by N2, C27, C28, C29, and N3 significantly
of the hydrogen resonance of the hydrogen atom present by 0.39 Å. A shortening of bonds can be observed between
in the former benzene ring. The dearomatized ring shows the silicon atom and the nitrogen atoms of the supporting
multiplets in the range of δ = 5.28–5.31 (1 H), 5.34–5.38 ligand. The average bond length between Si–Nav in 4 is
(1 H), 5.44–5.49 (1 H), and 5.96–5.99 (1 H) ppm, respec-
1
tively, in its H NMR spectrum. These values support the
dearomatization of the benzene ring and are in agreement
with those reported in the literature.[23] The mass spectrum
of compound 4 displays its molecular ion peak at m/z 625.3
confirming the composition.
Scheme 3. Synthesis of 4.
Product 4 was unambiguously identified by single-crystal Figure 3. Molecular structure of 4, where the substituents on the
N atoms and hydrogen on the carbon atoms except on C1, C26,
and C30 have been deleted for clarity. The hydrogen on C1 was
X-ray structural analysis. Product 4 crystallizes in the tri-
clinic space group P1 and the molecular structure is shown
¯
found and refined freely. Selected bond lengths [Å] and angles [°]:
Si(1)–N(1) 1.780(2), Si(1)–N(2) 1.720(2), Si(1)–N(3) 1.728(2), Si(1)–
C(1) 1.877(3), C(1)–C(2) 1.477(4), C(2)–C(3) 1.329(4), C(3)–C(4)
1.465(4), C(4)–C(5) 1.339(4), C(5)–C(6) 1.441(3), C(6)–C(7)
1.341(3), C(7)–N(1) 1.406(3), C(6)–C(1) 1.512(3); N(1)–Si(1)–N(3)
113.96(10), N(2)–Si(1)–N(3) 103.36(9), N(1)–Si(1)–N(2) 115.11(10),
N(3)–Si(1)–C(1) 111.18(12), N(2)–Si(1)–C(1) 120.85(12), N(1)–
Si(1)–C(1) 92.79(10), Si(1)–C(1)–C(2) 128.60(2), C(6)–C(1)–C(2)
in Figure 3. The imine compound (–N=C–C) has been con-
verted into the alkene derivative (–N–C=C–). We propose
that the reaction of LЈ with N-benzylideneaniline follows
the [1+4]-cycloaddition reaction (Scheme 4). The silicon
atom, which is already part of the C3N2Si six-membered
ring based on LЈ, acts as a reaction center to form a new
C3NSi five-membered ring with the N-benzylideneaniline 112.2(2).
Scheme 4. Proposed mechanism for the formation of 4.
Eur. J. Inorg. Chem. 2011, 5006–5013
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5009

H. W. Roesky et al.
FULL PAPER
1.724(2) Å, whereas in LЈ it is 1.7345(10) Å. In addition, other hand, the reaction of N2O allows the formation of
there is an appreciable change in the N–Si–N bite angle at silanones with a facile removal of N2, henceforth providing
the silicon atom with the backbone ligand. In 4 it is ample steric clearance for subsequent trimerization to oc-
103.36(9)°, whereas in LЈ it is 99.317(54)°. The bond lengths cur, furnishing the six-membered Si3O3 species. The origin
of Si1–N1 and Si1–C1 are 1.780(2) and 1.877(3) Å, indicat- of extra stabilization of 1c can be explained through the
ing single bond character.[20] The bond lengths between ad- steric strain imposed on the four-membered ring species
jacent carbon atoms in the dearomatized six-membered 1ac. The average bond angles O–Si–O and Si–O–Si are
benzene ring (C1, C2, C3, C4, C5, C6) of compound 4 pos- 100.3 and 135.9° in case of 1c while for 1ac they are 85.2
sess both single and double bond character, the bond and 94.8°, respectively. These values clearly indicate an in-
lengths between C1–C2, C3–C4, C5–C6, and C1–C6 are herent ring strain present in 1ac. To further quantify the
1.477(4), 1.465(4), 1.441(3), and 1.512(3) Å indicating C–C higher ring strain we have compared the energies of the O–
single bonds and the bond lengths between C2–C3 and C4– Si[(tBuN)2CPh]–O (F1) and PhC(NtBu)2Si–O–Si(NtBu)2-
C5 are 1.329(4) and 1.339(4) Å representing C=C double CPh (F2) fragments from the gas-phase optimized 1c and
bonds. The bond lengths of C7–N1 and N1–C8 are 1.406(3) 1ac structures, respectively (see Figure S1 and Scheme S1
and 1.416(3) Å, respectively. The bond length between C6– for fragment definition). Both fragments are relatively
C7 is 1.341(3) Å and thus reflects a C=C double bond.[22]
stable for 1c with higher stability of F2, as a direct conse-
BP86/SVP optimized structures of the trimer containing quence of the more relaxed ЄSi–O–Si bond angle (see Fig-
a Si3O3 six-membered unit (1c) and a dimer containing a ure 4).
Si2O2 four-membered unit (1ac) are shown in Figure 4. Both
Additional DFT calculations were performed to eluci-
the DFT-optimized structures display a good resemblance date the driving force for the formation of dearomatized
with the X-ray crystal data. The reaction of L with N2O [1+4]-cycloaddition product 4c. The isomeric [1+2]-cycload-
affords 1c, the process being highly favorable with a reaction dition product (4ic) is not observed when LЈ reacts with an
energy of –1285.6 kJ/mol at BP86/TZVP//BP86/SVP level equimolar amount of N-benzylideneaniline. DFT-opti-
of theory (see Computational Details). It was previously mized structures of 4c and 4ic are depicted in Figure 5. Cal-
reported that the reaction of L with tert-butylisocyanate in culations reveal that the [1+4]-cycloaddition product is en-
toluene at ambient temperature furnishes a four-membered ergetically more stable by 16.4 kJ/mol compared to the
Si2O2 ring species (1ac).[13g] Interestingly, the formation of [1+2]-cycloaddition product. The activation energy for the
the Si2O2 four-membered ring is not observed in the pres- formation of both 4c and 4ic were calculated at the BP86/
ence of N2O, instead a paddle-wheel like Si3O3 six-mem- SVP level of theory (see Computational Details). For 4c the
bered ring is formed (vide supra). We envisage that the cy- activation barrier is 47.9 kJ/mol lower than for 4ic indicat-
clization of the silanones formed from tert-butylisocyanate ing a more facile formation of the [1+4]-cycloaddition prod-
is controlled by the sterically hindered tert-butyl groups. uct. The LUMO of 4c is predominantly the pz orbital of
While the approach of more than two such silanone units silicon, which is perpendicular to the LЈ plane and is elec-
seems to be prohibitive, the exclusive formation of the four- trophilic in nature.[27] Preferential orbital interaction will be
membered Si2O2 fragment is nevertheless observed. On the sustained only when the orbitals of the ligands are oriented
for better overlap. For the formation of 4ic the pz orbital has
Figure 4. BP86/SVP-optimized structures of the compounds 1c and
1ac with bond lengths [Å] and bond angles [°]. Hydrogen atoms
are omitted for clarity. Values in parentheses represent X-ray data.
Figure 5. BP86/SVP-optimized structures of compounds 4c and 4ic
with bond lengths [Å] and bond angles [°]. Hydrogen atoms are
omitted for clarity.
5010
www.eurjic.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 5006–5013

Reactions of Stable Amidinate Chlorosilylene
Synthesis of 1: Toluene (60 mL) was added to a 100-mL Schlenk
flask containing L (0.31 g, 1.05 mmol). Gaseous N2O was passed
through the solution for 10 min. After that, the solvent was com-
pletely removed and the compound redissolved in hexane (30 mL).
The solution was filtered, and the filtrate was reduced in vacuo to
15 mL and stored in a freezer at –32 °C for a day to obtain colorless
single crystals of 1, yield 0.27 g, 82.0%, m.p. 220–223 °C. For ele-
mental analysis, 1·0.5hexane was treated under vacuum for 6 h to
remove the n-hexane molecules. C45H69Cl3N6O3Si3 (930.38): calcd.
been distorted to allow orbital overlaps with the adjacent
N and C atoms furnishing a N–Si–C three-membered unit
concomitant with a reduced N–Si–C bond angle of 48°.[28]
However, a similar orbital distortion is not conceptualized
in the [1+4]-cycloaddition product 4c, where the interac-
tions from the N and Cortho atoms are more “opened” (N–
Si–C bond angle: 92°). This particular regulation in orbital
orientation allows the stabilization of the [1+4]-cycload-
dition product 4c. Another important observation emanates
1
C 57.95, H 7.46, N 9.01; found C 57.85, H 7.82, N 8.80. H NMR
from the fact that the relative conformation of the N- (200 MHz, C6D6, 25 °C): δ = 1.45 [br. s, 54 H, C(CH3)3], 6.80–6.99
(br., 15 H, C6H5) ppm. 29Si{1H} NMR (99.36 MHz, C6D6, 25 °C):
benzylideneaniline fragments in complexes 4c and 4ic are
δ = –114.51 ppm. EI-MS: m/z (%) = 629 [M+ – {PhC(NtBu)2
2Cl}], 594 [M+ – {PhC(NtBu)2 + 3Cl}].
+
considerably different from its free form. The conforma-
tional deformation of the complexed LЈ fragment with re-
spect to the DFT-optimized LЈ structure is more pro-
nounced in 4c than 4ic (ΔEe ≈ 63 kJ/mol). This indicates
Synthesis of 2: To a Schlenk flask containing L (0.30 g, 1.02 mmol)
in toluene (30 mL) cooled to –78 °C, B(C6F5)3 (0.52 g, 1.02 mmol)
the combined effect of two factors: firstly, favorable orbital dissolved in toluene (30 mL) was added. The stirred reaction mix-
ture was warmed to room temperature and stirred for another 12 h.
The solution was filtered and the solvent was reduced in vacuo to
15 mL and stored in a freezer at –32 °C for 3 days to obtain color-
less single crystals of 2, yield 0.65 g, 79.3%, m.p. 195–198 °C (dec.).
C33H23BClF15N2Si (806.87): calcd. C 49.12, H 2.87, N 3.47; found
C 48.95, H 2.83, N 3.41. 1H NMR (300 MHz, C6D6, 25 °C): δ =
0.65 [s, 18 H, C(CH3)3], 6.57–6.85 (br., 5 H, C6H5) ppm. 19F{1H}
NMR (282.40 MHz, C6D6, 25 °C): δ = –125.38 (m), –157.47 (m),
–167.73 (m) ppm. 11B{1H} NMR (96.29 MHz, C6D6, 25 °C): δ =
–17.55 ppm. 29Si{1H} NMR (59.63 MHz, C6D6, 25 °C): δ = 29.94
(br) ppm. ESI-MS: m/z (%) = 638 [M+ – C6F5].
interaction (vide supra) and secondly, ring strain relief pre-
dominates in the ligand deformation calculated for 4c al-
lowing its formation to be more feasible than that of 4ic.
Conclusions
In summary, we first explored the reactivity of chlorosil-
ylene, PhC(NtBu)2SiCl (L) with N2O, which afforded the
trimer {PhC(NtBu)2Si(O)Cl}3 (1), containing a Si3O3 six-
membered ring. In 1, the PhC(NtBu)2 and Cl moieties are
aligned in opposite directions of the plane. In addition we
reported the chlorosilylene–boron adducts L·B(C6F5)3 (2)
and L·9-BBN (3), yielded by the reaction of L with
B(C6F5)3 and 9-BBN. The reaction of CH{(C=CH2)(CMe)-
(2,6-iPr2C6H3N)2}Si (LЈ) with N-benzylideneaniline af-
forded 4 as a [1+4]- rather than a [1+2]-cycloaddition prod-
uct. Here the reaction occurred at the silicon atom, and a
new five-membered ring was formed leading to a spirocyclic
compound keeping the C3N2Si six-membered ring intact.
Formation of products 1 and 4 was supported by DFT cal-
culations.
Synthesis of 3: To a Schlenk flask containing L (0.30 g, 1.02 mmol)
in toluene (30 mL) was added 0.5 m 9-BBN(THF) solution (2 mL,
1.00 mmol) at –78 °C. The stirred reaction mixture was warmed to
room temperature and stirred for another 12 h. The solution was
filtered and the solvent was reduced in vacuo to 20 mL and stored
in a freezer at –32 °C for 14 h to obtain crystalline compound 3,
yield 0.33 g, 78.6%, m.p. 202–205 °C (dec.). C23H38BClN2Si
(416.26): calcd. C 66.26, H 9.19, N 6.72; found C 66.16, H 9.14, N
6.68. 1H NMR (500 MHz, C6D6, 25 °C): δ = 1.01 [s, 18 H,
C(CH3)3], 6.71–6.90 (br.,
5
H, C6H5) ppm. 11B{1H} NMR
(96.29 MHz, C6D6, 25 °C): δ = –15.04 (d, JBH = 70 Hz) ppm.
29Si{1H} NMR (99.36 MHz, C6D6, 25 °C): δ = 29.62 (br) ppm.
FTIR (Nujol): νB–H 2193(w). ESI-MS: m/z (%) = 416 [M+], 381
[M+ – Cl].
Synthesis of 4: To a Schlenk flask containing LЈ (0.25 g, 0.56 mmol)
in hexane (30 mL) cooled to –78 °C, N-benzylideneaniline (0.10 g,
0.55 mmol) dissolved in hexane (30 mL) was added. The stirred
reaction mixture was warmed to room temperature and stirred for
another 12 h. The solution was filtered and the solvent was reduced
Experimental Section
General: Syntheses were carried out under an inert atmosphere of
dinitrogen in oven-dried glassware using standard Schlenk tech- in vacuo to 20 mL and stored in a freezer at –32 °C for 3 days to
niques and other manipulations were accomplished in a dinitrogen-
filled glove box. Solvents were purified by the MBRAUN solvent
purification system MB SPS-800. All chemicals were purchased
from Aldrich and used without further purification. L[3a,3c] and
LЈ[3d] were prepared as reported in the literature. 1H and 29Si NMR
spectra were recorded with a Bruker Avance DPX 200, or a Bruker
Avance DRX 500 spectrometer, using C6D6 as solvent. Chemical
shifts δ are given relative to SiMe4. EI-MS spectra were obtained
with a Finnigan MAT 8230 instrument and ESI-MS spectra with
an Applied Biosystems API 2000 as well as with a Thermo Finni-
gan Ion Trap LCQ spectrometer. Elemental analyses were per-
formed by the Institut für Anorganische Chemie, Universität
Göttingen. Melting points were measured in sealed glass capillaries
on a Büchi B-540 melting point apparatus.
obtain colorless single crystals of 4, yield 0.26 g, 74%, m.p. 168–
170 °C. C42H51N3Si (625.39): calcd. C 80.59, H 8.21, N 6.71; found
C 79.52, H 9.07, N 6.58. 1H NMR (500 MHz, CD6, 25 °C): δ = 0.76
[d, J = 7 Hz, 3 H, CH(CH3)2], 0.87 [d, J = 7 Hz, 3 H, CH(CH3)2],
1.02 [d, J = 7 Hz, 3 H, CH(CH3)2], 1.18 [d, J = 7 Hz, 3 H,
CH(CH3)2], 1.28–1.31 [2ϫ d, 6 H, CH(CH3)2], 1.40–1.49 [m, 9 H,
CH(CH3)2, NCCH3], 3.08 (m, 1 H, SiCH), 3.14 [m, J = 7 Hz, 1 H,
CH(CH3)2], 3.33–3.38 [m, 2 H, CH(CH3)2, NCCH2], 3.68 [m, J =
7 Hz, 1 H, CH(CH3)2], 3.96–4.01 [m, 2 H, CH(CH3)2, NCCH2],
5.28–5.31 (m, 1 H, CH), 5.34–5.38 (m, 1 H, CH), 5.44–5.49 (m, 2
H, CH, γ-CH), 5.66 (s, 1 H, NCH), 5.96–5.99 (m, 1 H, CH), 6.88–
7.29 (m, 11 H, C6H5, 2ϫ iPr2C6H3) ppm. 29Si{1H} NMR
(99.36 MHz, C6D6, 25 °C): δ = –25.40 ppm. EI-MS: m/z (%) =
625.3 [M+].
Eur. J. Inorg. Chem. 2011, 5006–5013
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5011

H. W. Roesky et al.
FULL PAPER
3948–3950; b) R. S. Ghadwal, H. W. Roesky, S. Merkel, J.
Henn, D. Stalke, Angew. Chem. 2009, 121, 5793–5796; Angew.
Chem. Int. Ed. 2009, 48, 5683–5686; c) S. S. Sen, H. W. Roesky,
D. Stern, J. Henn, D. Stalke, J. Am. Chem. Soc. 2010, 132,
1123–1126; d) M. Driess, S. Yao, M. Brym, C. van Wüllen, D.
Lentz, J. Am. Chem. Soc. 2006, 128, 9628–9629; e) L. Kong, J.
Zhang, H. Song, C. Cui, Dalton Trans. 2009, 39, 5444–5446.
a) R.-E. Li, J.-H. Sheu, M.-D. Su, Inorg. Chem. 2007, 46, 9245–
9253; b) P. V. Bharatam, R. Moudgil, D. Kaur, Inorg. Chem.
2003, 42, 4743–4749; c) P. V. Bharatam, R. Moudgil, D. Kaur,
Organometallics 2002, 21, 3683–3690.
a) M. Haaf, R. Hayashi, R. West, J. Chem. Soc., Chem. Com-
mun. 1994, 33–34; b) R. West, M. Denk, Pure Appl. Chem.
1996, 68, 785–788; c) J. D. Feldman, G. P. Mitchell, J.-O. Nolte,
T. D. Tilley, J. Am. Chem. Soc. 1998, 120, 11184–11185; d) B.
Gehrhus, P. B. Hitchcock, M. F. Lappert, H. Maciejewski, Or-
ganometallics 1998, 17, 5599–5601; e) W. Yang, H. Fu, H.
Wang, M. Chen, Y. Ding, H. W. Roesky, A. Jana, Inorg. Chem.
2009, 48, 5058–5060; f) S. H. A. Petri, D. Eikenberg, B. Neum-
ann, H.-G. Stammler, P. Jutzi, Organometallics 1999, 18, 2615–
2618; g) T. A. Schmedake, M. Haaf, B. J. Paradise, D. Powell,
R. West, Organometallics 2000, 19, 3263–3265; h) J. M. Dysard,
T. D. Tilley, Organometallics 2000, 19, 4726–4732; i) S. B.
Clendenning, B. Gehrhus, P. B. Hitchcock, D. F. Moser, J. F.
Nixon, R. West, J. Chem. Soc., Dalton Trans. 2002, 484–490;
j) D. Amoroso, M. Haaf, G. P. A. Yap, R. West, D. E. Fogg,
Organometallics 2002, 21, 534–540; k) A. Meltzer, C. Präsang,
M. Driess, J. Am. Chem. Soc. 2009, 131, 7232–7233; l) A. G.
Avent, B. Gehrhus, P. B. Hitchcock, M. F. Lappert, H. Macie-
jewski, J. Organomet. Chem. 2003, 686, 321–331; m) Y. Xiong,
S. Yao, M. Driess, Inorg. Chem. 2009, 48, 7522–7524.
S. Yao, C. van Wüllen, X.-Y. Sun, M. Driess, Angew. Chem.
2008, 120, 3294–3297; Angew. Chem. Int. Ed. 2008, 47, 3250–
3253.
Crystal Structure Determination: Suitable single crystals for X-ray
structural analyses of 1, 2, and 4 were mounted on a glass fiber,
and the respective data were collected with an IPDS II Stoe image-
plate diffractometer (graphite-monochromated Mo-Kα radiation, λ
= 0.71073 Å) at 133(2) K. The structures were solved by direct
methods (SHELXS-97) and refined against all data by full-matrix
least-squares methods on F2 (SHELXL-97).[29] All non-hydrogen
atoms were refined with anisotropic displacement parameters. The
hydrogen atoms were refined isotropically at calculated positions
using a riding model with their Uiso values constrained to 1.5 Ueq
of their pivot atoms for terminal sp3 carbon atoms and 1.2 times
for all other carbon atoms. In compound 4 the hydrogen atoms on
carbons C1 to C5 and on C7 were found and refined freely without
any restraints, though their Uiso values were refined jointly.
[4]
[5]
CCDC-831714 (for 1), -831715 (for 2), and -776752 (for 4) contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Computational Details: All calculations were performed in
Gaussian03 quantum code.[30] The geometries of all compounds
were optimized with the generalized approximation (GGA) to DFT
by using the exchange functional of Becke[31] in addition to the
correlation functional of Perdew[32] (BP86). All the atoms were
treated with Ahlrich’s split valence plus polarization (SVP) basis
sets[33] of 6-31G* quality. In all our DFT treatments, the resolution-
of-the-identity (RI) approximation (also called “density fitting”)
for the two electron integrals was employed.[34] The geometries were
optimized without any symmetry constraints. For validation, sin-
gle-point energies were calculated with larger basis sets at BP86/
TZVP[35] using BP86/SVP-optimized geometries. Relative energies
in this work are given at the BP86/TZVP//BP86/SVP level of theory
if otherwise not mentioned. Approximate activation energy was cal-
culated by investigating the potential energy surface scan of a speci-
fied reaction coordinate. NMR shielding tensors were calculated
for the selected optimized structures using the Gauge-Independent
Atomic Orbital (GIAO) method.[30] All figures were made in the
Chemcraft visualization software.[36]
[6]
[7]
a) A. Meltzer, S. Inoue, C. Präsang, M. Driess, J. Am. Chem.
Soc. 2010, 132, 3038–3046; b) A. Jana, C. Schulzke, H. W. Roe-
sky, J. Am. Chem. Soc. 2009, 131, 4600–4601; c) A. Jana, H. W.
Roesky, C. Schulzke, P. P. Samuel, Organometallics 2009, 28,
6574–6577.
a) S. Yao, M. Brym, C. van Wüllen, M. Driess, Angew. Chem.
2007, 119, 4237–4240; Angew. Chem. Int. Ed. 2007, 46, 4159–
4162; b) B. Gehrhus, P. B. Hitchcock, M. F. Lappert, J. Hein-
icke, R. Boese, D. Bläser, J. Organomet. Chem. 1996, 521, 211–
220; c) M. Haaf, A. Schmiedl, T. A. Schmedake, D. R. Powell,
A. J. Millevolte, M. Denk, R. West, J. Am. Chem. Soc. 1998,
120, 12714–12719.
[8]
Supporting Information (see footnote on the first page of this arti-
cle): DFT-optimized geometries (Cartesian coordinates) and abso-
lute energies.
[9]
Y. Xiong, S. Yao, M. Brym, M. Driess, Angew. Chem. 2007,
119, 4595–4597; Angew. Chem. Int. Ed. 2007, 46, 4511–4513.
a) B. Gehrhus, P. B. Hitchcock, M. F. Lappert, J. C. Slootweg,
Chem. Commun. 2000, 1427–1428; b) F. Antolini, B. Gehrhus,
P. B. Hitchcock, M. F. Lappert, J. C. Slootweg, Dalton Trans.
2004, 3288–3294.
Acknowledgments
[10]
We are thankful to the Deutsche Forschungsgemeinschaft (DFG)
for supporting this work. R. A. is thankful to the Alexander von
Humboldt Stiftung for a research fellowship. D. K. acknowledges
Prof. S. Ramakrishnan and Prof. S. Dattagupta for constant sup-
port and encouragement. D. K. is indebted to Prof. B. M. Deb and
Dr. R. K. Nayak for providing computational facilities.
[11]
[12]
Y. Xiong, S. Yao, M. Driess, Organometallics 2009, 28, 1927–
1933.
C. Präsang, M. Stoelzel, S. Inoue, A. Meltzer, M. Driess, An-
gew. Chem. 2010, 122, 10199–10202; Angew. Chem. Int. Ed.
2010, 49, 10002–10005.
[13]
a) Y. Xiong, S. Yao, M. Driess, Chem. Eur. J. 2009, 15, 5545–
5551; b) Y. Xiong, S. Yao, M. Driess, Organometallics 2010,
29, 987–990; c) S. B. Clendenning, B. Gehrhus, P. B. Hitchcock,
J. F. Nixon, Chem. Commun. 1999, 2451–2452; d) B. Gehrhus,
P. B. Hitchcock, Organometallics 2004, 23, 2848–2849; e) S. Ish-
ida, T. Iwamoto, M. Kira, Organometallics 2010, 29, 5526–
5534; f) J. Heinicke, B. Gehrhus, J. Organomet. Chem. 1992,
423, 13–21; g) S. Khan, S. S. Sen, D. Kratzert, G. Tavcˇar, H. W.
Roesky, D. Stalke, Chem. Eur. J. 2011, 17, 4283–4290; h) R.
Azhakar, S. P. Sarish, G. Tavcˇar, H. W. Roesky, J. Hey, D.
Stalke, D. Koley, Inorg. Chem. 2011, 50, 3028–3036.
[1] a) P. P. Gaspar, R. West, in: The Chemistry of Organic Silicon
Compounds (Eds.: Z. Rappoport, Y. Apeloig), John Wiley &
Sons, Chichester, 1998, vol. 2, part 3, p. 2463–2567; b) M.
Haaf, T. A. Schmedake, R. West, Acc. Chem. Res. 2000, 33,
704–714; c) B. Gehrhus, M. F. Lappert, J. Organomet. Chem.
2001, 617–618, 209–223; d) S. Nagendran, H. W. Roesky, Orga-
nometallics 2008, 27, 457–492.
[2] M. Denk, R. Lennon, R. Hayashi, R. West, A. V. Belyakov,
H. P. Verne, A. Haaland, M. Wagner, N. Metzler, J. Am. Chem.
Soc. 1994, 116, 2691–2692.
[3] a) C.-W. So, H. W. Roesky, J. Magull, R. B. Oswald, Angew.
Chem. 2006, 118, 4052–4054; Angew. Chem. Int. Ed. 2006, 45,
[14]
a) R. S. Ghadwal, R. Azhakar, K. Pröpper, J. J. Holstein, B.
Dittrich, H. W. Roesky, Inorg. Chem. 2011, 50, 8502–8508; b)
5012
www.eurjic.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 5006–5013

Reactions of Stable Amidinate Chlorosilylene
R. Azhakar, S. P. Sarish, H. W. Roesky, J. Hey, D. Stalke, Inorg.
Chem. 2011, 50, 5039–5043; c) G. Tavcˇar, S. S. Sen, R. Azhakar,
A. Thorn, H. W. Roesky, Inorg. Chem. 2010, 49, 10199–10202;
d) J. Li, S. Merkel, J. Henn, K. Meindl, A. Döring, H. W. Roe-
sky, R. S. Ghadwal, D. Stalke, Inorg. Chem. 2010, 49, 775–777.
[15] a) R. S. Ghadwal, H. W. Roesky, S. Merkel, D. Stalke, Chem.
Eur. J. 2010, 16, 85–88; b) R. Azhakar, G. Tavcˇar, H. W. Roe-
sky, J. Hey, D. Stalke, Eur. J. Inorg. Chem. 2011, 475–477.
[16] a) A. Jana, P. P. Samuel, G. Tavcˇar, H. W. Roesky, C. Schulzke,
J. Am. Chem. Soc. 2010, 132, 10164–10170; b) R. Azhakar, S. P.
Sarish, H. W. Roesky, J. Hey, D. Stalke, Organometallics 2011,
30, 2897–2900; c) R. Azhakar, R. S. Ghadwal, H. W. Roesky,
J. Hey, D. Stalke, Organometallics 2011, 30, 3853–3858.
[17] a) S. P. Nolan (Ed.), N-Heterocyclic Carbenes in Synthesis,
Wiley-VCH, Weinheim, Germany, 2006; b) F. Glorius (Ed.), N-
Heterocyclic Carbenes in Transition Metal Catalysis, Springer-
Verlag, Berlin, 2007; c) J. Chun, I. G. Jung, H. J. Kim, M. Park,
M. S. Lah, S. U. Son, Inorg. Chem. 2009, 48, 6353–6355; d) P.-
C. Chiang, M. Rommel, J. W. Bode, J. Am. Chem. Soc. 2009,
131, 8714–8718; e) V. J. Catalano, A. L. Moore, J. Shearer, J.
Kim, Inorg. Chem. 2009, 48, 11362–11375; f) N. D. Harrold,
R. Waterman, G. L. Hillhouse, T. R. Cundari, J. Am. Chem.
Soc. 2009, 131, 12872–12873; g) A. Sinha, S. M. W. Rahaman,
M. Sarkar, B. Saha, P. Daw, J. K. Bera, Inorg. Chem. 2009, 48,
11114–11122; h) A. G. Tennyson, E. L. Rosen, M. S. Collins,
V. M. Lynch, C. W. Bielawski, Inorg. Chem. 2009, 48, 6924–
6933; i) Y. Lee, B. Li, A. H. Hoveyda, J. Am. Chem. Soc. 2009,
131, 11625–11633; j) P. M. Zimmerman, A. Paul, C. B. Mus-
grave, Inorg. Chem. 2009, 48, 5418–5433; k) S. Groysman,
R. H. Holm, Inorg. Chem. 2009, 48, 621–627; l) E. M. Phillips,
M. Riedrich, K. A. Scheidt, J. Am. Chem. Soc. 2010, 132,
13179–13181; m) M. K. Samantaray, C. Dash, M. M. Shaikh,
K. Pang, R. J. Butcher, P. Ghosh, Inorg. Chem. 2011, 50, 1840–
1848; n) J. Mathew, C. H. Suresh, Inorg. Chem. 2010, 49, 4665–
4669; o) J. M. Smith, J. R. Long, Inorg. Chem. 2010, 49, 11223–
11230; p) F. E. Hahn, M. C. Jahnke, Angew. Chem. 2008, 120,
3166–3216; Angew. Chem. Int. Ed. 2008, 47, 3122–3172.
v. R. Schleyer, G. H. Robinson, Science 2008, 321, 1069–1071;
c) Y. Wang, Y. Xie, M. Y. Abraham, P. Wei, H. F. Schaefer III,
P. v. R. Schleyer, G. H. Robinson, J. Am. Chem. Soc. 2010, 132,
14370–14372; d) Y. Wang, G. H. Robinson, Chem. Commun.
2009, 5201–5213.
[20] S. S. Sen, G. Tavcˇar, H. W. Roesky, D. Kratzert, J. Hey, D.
Stalke, Organometallics 2010, 29, 2343–2347.
[21] S. P. Sarish, A. Jana, H. W. Roesky, P. P. Samuel, C. E. A. And-
rade, B. Dittrich, C. Schulzke, Organometallics 2011, 30, 912–
916.
[22] a) E. Otten, R. C. Neu, D. W. Stephan, J. Am. Chem. Soc. 2009,
131, 9918–9919; b) Y. Xiong, S. Yao, M. Driess, J. Am. Chem.
Soc. 2009, 131, 7562–7563; c) S. Yao, Y. Xiong, M. Brym, M.
Driess, J. Am. Chem. Soc. 2007, 129, 7268–7269; d) I. Bar-
Nahum, A. K. Gupta, S. M. Huber, M. Z. Ertem, C. J. Cramer,
W. B. Tolman, J. Am. Chem. Soc. 2009, 131, 2812–2814.
[23] a) J. García-Fortanet, F. Kessler, S. L. Buchwald, J. Am. Chem.
Soc. 2009, 131, 6676–6677; b) C. S. Penkett, J. A. Woolford,
I. J. Day, M. P. Coles, J. Am. Chem. Soc. 2010, 132, 4–5; c)
S. R. Wang, Z. Qiu, Z. Xie, J. Am. Chem. Soc. 2010, 132, 9988–
9989; d) K. L. Miller, B. N. Williams, D. Benitez, C. T. Carver,
K. R. Ogilby, E. Tkatchouk, W. A. Goddard III, P. L. Diacone-
scu, J. Am. Chem. Soc. 2010, 132, 342–355; e) S. Duhovic, M. J.
Monreal, P. L. Diaconescu, Inorg. Chem. 2010, 49, 7165–7169;
f) M. Feller, E. Ben-Ari, M. A. Iron, Y. Diskin-Posner, G. Le-
itus, L. J. W. Shimon, L. Konstantinovski, D. Milstein, Inorg.
Chem. 2010, 49, 1615–1625; g) G. Zeng, Y. Guo, S. Li, Inorg.
Chem. 2009, 48, 10257–10263.
[24] a) A. W. Addison, T. N. Rao, J. Reedijk, J. van Rijn, G. C. Ver-
schoor, J. Chem. Soc., Dalton Trans. 1984, 1349–1356; b) V.
Chandrasekhar, R. Azhakar, T. Senapati, P. Thilagar, S. Ghosh,
S. Verma, R. Boomishankar, A. Steiner, P. Kögerler, Dalton
Trans. 2008, 1150–1160.
[25] a) C. Ackerhans, H. W. Roesky, T. Labahn, J. Magull, Organo-
metallics 2002, 21, 3671–3674; b) M. Unno, Y. Kishimoto, H.
Matsumoto, Organometallics 2004, 23, 6221–6224; c) Y. Itami,
B. Marciniec, M. Kubicki, Organometallics 2003, 22, 3717–
3722.
[18] a) D. P. Mills, L. Soutar, W. Lewis, A. J. Blake, S. T. Liddle, J.
Am. Chem. Soc. 2010, 132, 14379–14381; b) C.-H. Yang, J. Bel-
tran, V. Lemaur, J. Cornil, D. Hartmann, W. Sarfert, R.
Fröhlich, C. Bizzari, L. D. Cola, Inorg. Chem. 2010, 49, 9891–
9901; c) H.-J. Park, K. H. Kim, S. Y. Choi, H.-M. Kim, W. I.
Lee, Y. K. Kang, Y. K. Chung, Inorg. Chem. 2010, 49, 7340–
7352; d) R. S. Crees, M. L. Cole, L. R. Hanton, C. J. Sumby,
Inorg. Chem. 2010, 49, 1712–1719; e) C. Dash, M. M. Shaikh,
R. J. Butcher, P. Ghosh, Inorg. Chem. 2010, 49, 4972–4983; f)
C.-F. Fu, C.-C. Lee, Y.-H. Liu, S.-M. Peng, S. Warsink, C. J.
Elsevier, J.-T. Chen, S.-T. Liu, Inorg. Chem. 2010, 49, 3011–
[26] H. C. Brown, B. Singaram, C. P. Mathew, J. Org. Chem. 1981,
46, 2712–2717.
[27] M.-D. Su, S.-Y. Chu, Inorg. Chem. 1999, 38, 4819–4823.
[28] We have optimized compound 4 (S. P. Sarish, A. Jana, H. W.
Roesky, P. P. Samuel, C. E. A. Andrade, B. Dittrich, C. Schul-
zke, Organometallics 2011, 30, 912–916.) at BP86/SVP level and
the N–Si–C cone angle was found to be 48°. Unlike 4c, the
HOMO in 4 is mainly the lone-pair orbital on silicon and hence
it might be a nucleophilic center.
[29] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
3018; g) S. Naeem, L. Delaude, A. J. P. White, J. D. E. T. Wil- [30] M. J. Frisch et al., Gaussian 03, revision E.01, Gaussian, Inc.,
ton-Ely, Inorg. Chem. 2010, 49, 1784–1793; h) W.-Q. Zhang,
A. C. Whitwood, I. J. S. Fairlamb, J. M. Lynam, Inorg. Chem.
2010, 49, 8941–8952; i) F. Huang, G. Lu, L. Zhao, Z.-X. Wang,
Wallingford CT, 2004 (for the complete list of authors see Sup-
porting Information).
[31] A. D. Becke, Phys. Rev. A 1988, 38, 3098–3100.
J. Am. Chem. Soc. 2010, 132, 12388–12396; j) C.-H. Hsieh, [32] a) J. P. Perdew, Phys. Rev. B 1986, 33, 8822–8824; b) J. P. Per-
M. Y. Darensbourg, J. Am. Chem. Soc. 2010, 132, 14118–
14125; k) P. Arnold, S. Pearson, Coord. Chem. Rev. 2007, 251,
596–609; l) M. Albrecht, Chem. Commun. 2008, 3601–3610; m)
K. E. Krahulic, H. M. Tuononen, M. Parvez, R. Roesler, J.
Am. Chem. Soc. 2009, 131, 5858–5865; n) L. Benhamou, E.
Chardon, G. Lavigne, S. Bellemin-Laponnaz, V. César, Chem.
Rev. 2011, 111, 2705–2733.
dew, Phys. Rev. B 1986, 34, 7406–7406.
[33] A. Schäfer, H. Horn, R. Ahlrichs, J. Chem. Phys. 1992, 97,
2571–2577.
[34] a) B. I. Dunlap, J. Chem. Phys. 1983, 78, 3140–3142; b) B. I.
Dunlap, THEOCHEM 2000, 529, 37–40.
[35] F. Weigend, R. Ahlrichs, Phys. Chem. Chem. Phys. 2005, 7,
3297–3305.
[19] a) B. Quillian, P. Wei, C. S. Wannere, P. v. R. Schleyer, G. H.
Robinson, J. Am. Chem. Soc. 2009, 131, 3168–3169; b) Y.
Wang, Y. Xie, P. Wei, R. B. King, H. F. Schaefer III, P.
[36] http://www.chemcraftprog.com/index.html.
Received: June 29, 2011
Published Online: October 10, 2011
Eur. J. Inorg. Chem. 2011, 5006–5013
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5013